Bryophyte

The bryophytes are those embryophyte plants ('land plants') that are non-vascular: they have tissues and enclosed reproductive systems, but they lack vascular tissue that circulates liquids. They neither flower nor produce seeds, reproducing via spores.

Bryophyte classification

The bryophytes do not form a monophyletic group but consist of three groups, the Marchantiophyta (liverworts), Anthocerotophyta (hornworts), and Bryophyta (mosses).

Two hypotheses on the phylogeny of land plants (embryophyta).

Modern studies of the land plants generally show one of two patterns. In one of these patterns, the liverworts were the first to diverge, followed by the hornworts, while the mosses are the closest living relatives of the polysporangiates (which include the vascular plants). In the other pattern, the hornworts were the first to diverge, followed by the vascular plants, while the mosses are the closest living relatives of the liverworts. Originally the three groups were brought together as the three classes of division Bryophyta. However, since the three groups of bryophytes form a paraphyletic group, they now are placed in three separate divisions.

Bryophyte sexuality

These plants are generally gametophyte-oriented; that is, the normal plant is the haploid gametophyte, with the only diploid structure being the sporangium in season. As a result, bryophyte sexuality is very different from that of other plants. There are two basic categories of sexuality in bryophytes:

• Dioicous bryophytes produce only antheridia (male organs) or archegonia (female organs) on a single plant body.
• Monoicous bryophytes produce both antheridia and archegonia on the same plant body.

Some bryophyte species may be either monoicous or dioicous depending on environmental conditions. Other species grow exclusively with one type of sexuality.

Notice that these terms are not the same as monoecious and dioecious, which refer to whether or not a sporophyte plant bears one or both kinds of gametophyte. Those terms apply only to seed plants.

See also

• Embryophyte
• Marchantiophyta (liverworts)
• Anthocerotophyta (hornworts)
• Bryophyta (mosses)
• Plant sexuality

References

• Chopra, R. N. & Kumra, P. K. (1988). Biology of Bryophytes. New York: John Wiley & Sons. ISBN 0-470-21359-0.
• Crum, Howard (2001). Structural Diversity of Bryophytes. Ann Arbor: University of Michigan Herbarium. ISBN 0-9620733-4-2.
• Goffinet, Bernard. (2000). Origin and phylogenetic relationships of bryophytes. In A. Jonathan Shaw & Bernard Goffinet (Eds.), Bryophyte Biology, pp. 124-149. Cambridge: Cambridge University Press. ISBN 0-521-66097-1.
• Oostendorp, Cora (1987). The Bryophytes of the Palaeozoic and the Mesozoic. Bryophytorum Bibliotheca, Band 34. Berlin & Stuttgart: J. Cramer. ISBN 3-443-62006-X.
• Prihar, N. S. (1961). An Introduction to Embryophyta: Volume I, Bryophyta (4th ed.). Allahabad: Central Book Depot.
• Raven, Peter H., Evert, Ray F., & Eichhorn, Susan E. (2005). Biology of Plants (7th ed.). New York: W. H. Freeman and Company. ISBN 0-7167-1007-2.
• Schofield, W. B. (1985). Introduction to Bryology. New York: Macmillan. ISBN 0-02-949660-8.
• Watson, E. V. (1971). The Structure and Life of Bryophytes (3rd ed.). London: Hutchinson University Library. ISBN 0-09-109301-5.